Influence of cytotoxic butyltin complexes with 2-sulfobenzoic acid on the thermotropic phase behavior of lipid model membranes

Abstract

In the previous study, we showed that butyltin complexes with 2-sulfobenzoic acid (commonly referred to as BTsbz) exhibit a very wide biological activity. The BTsbz in vitro are very active cytotoxic agents against tumor cells—more effective than cisplatin and carboplatin (traditional anticancer drugs). These complexes are antibacterial agents against gram-positive and gram-negative bacteria, as well. The aim of the present study was to investigate the influence of BTsbz on the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) model membranes. The effect of this compound on the multilamellar liposomes was studied mainly by the means of differential scanning calorimetry and additionally by the steady-state fluorimetry and infrared spectroscopy. All investigated butyltin complexes with 2-sulfobenzoic acid change the thermotropic properties of lipid model membranes: The temperature of the main phase transition of DPPC is slightly decreased, and the transition’s cooperativity of the peak is very much reduced. With increasing concentration, all investigated compounds abolished the pretransition. The results suggest that BTsbz are very active in the hydrophilic area of DPPC bilayer and at the same time have an effect on membrane fluidity.